Poly(A) signals and transcriptional pause sites combine to prevent interference between RNA polymerase II promoters

EMBO J. 1993 Jun;12(6):2539-48. doi: 10.1002/j.1460-2075.1993.tb05909.x.


Transcriptional termination by RNA polymerase II at the 3' end of genes encoding poly(A)+ mRNAs is thought to require two distinct cis-active elements: a functional poly(A) signal and a downstream transcriptional pause site. An important requirement for efficient termination is to prevent transcriptional interference of downstream-located promoters. We have therefore investigated whether these two elements, individually or in combination, can prevent transcriptional interference of RNA polymerase II-activated promoters. For this purpose, we constructed an expression plasmid containing two tandem retroviral long terminal repeats (LTRs) derived from HIV-1. When transfected into HeLa cells, this construct resulted in transcriptional interference of the LTR promoters. Using this assay, we were able to show that a single poly(A) signal was able to protect an otherwise occluded promoter. This effect depended on the RNA-processing strength of the poly(A) signal. Furthermore, transcriptional pause sites provided adequate protection against promoter occlusion even when tested alone. Finally, a combined element consisting of a poly(A) signal followed by a pause site was more efficient in promoter protection than either element on its own. These results indicate that an interference-blocking element can take various forms: a poly(A) signal, a transcriptional pause site or a combination of both.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • HIV Long Terminal Repeat
  • HIV-1 / genetics
  • HeLa Cells
  • Humans
  • Plasmids
  • Poly A / metabolism*
  • Promoter Regions, Genetic*
  • RNA Polymerase II / genetics*
  • Terminator Regions, Genetic*


  • Poly A
  • RNA Polymerase II